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View Full Version : Bonnett Short Bubble (62) vs long Bubble



MrAlex
11-12-2004, 12:33 PM
I recently purchased a 64 TR4 (really a 63) to restore, and also aquired a 63 TR4 (really a 62) as a parts car from the original owner. I noticed that the bubble on the hood on the 62 is shorter than the 63 is. The 62 has the better hood so it's the one I will probably use. My question is does anyone know why they changed the bubble or any other info / factoids about the bubbles? This is mostly out of interest and education for me... Thanks

Mickey Richaud
11-12-2004, 01:24 PM
Hi Mr. Alex -

Welcome to the Forum! I'm sure you'll find lots of info here, whether you need it or not!

In looking at Bill Piggot's book, Original Triumph TR, he says that there were four different bonnets for the TR4-5. Up to car # CT6429, sometime in 1962 (the first '63 was believed to be # CT18605), there was a short "power bulge" (no snickers out there, please!), then until # CT37689 the bulge went almost to the rear of the bonnet. Later bonnets were basically the same, but with minor detail differences.

I recommend your getting a copy of his book - great tool for restoration, as well as general knowledge.

Mickey

Geo Hahn
11-12-2004, 01:57 PM
[ QUOTE ]
...My question is does anyone know why they changed the bubble or any other info / factoids about the bubbles?

[/ QUOTE ]

The bubble was there originally to provide clearance for the SU carbs. I believe they lengthened the bubble to stiffen the bonnet. Over-enthusiastic owners were bending the sheet metal when closing the bonnet by pressing on the right rear corner.

They kept the bubble for this reason (and they liked that 'power-bulge' thing) even though the later cars with (lower) ZS carbs would not have required any bubble for clearance.

TRTEL
11-14-2004, 12:42 PM
Another major design flaw of the short bubble was if the engine diesels at all (a not uncommon problem with cars that did not see the highway enough) the rear SU will leave a very nasty calling card on the sheet metal as the engine violently comes to a halt.

MDCanaday
11-15-2004, 10:44 PM
My 63 has the long bubble at ct14275, It was stammped on april 26 1962.I know because under the factory primer was a watermark"the Abby Metalworks LTD, The Welch Dragon"with a characture of a dragon on wheels. It looked too cool to just sand off, so I got some good pics of it. I intend to get an image system soon and will put this on a post.
MD(mad dog)